(1) Field of the Invention
The present invention relates to an apparatus and a method for using radio communication from a submerged underwater vehicle and more particularly to an apparatus and method for briefly surfacing an antenna towed behind an underwater vehicle.
(2) Description of the Prior Art
The characteristics of many radio frequencies do not allow communication through water from a submerged underwater vehicle. Extremely low frequency radio bands can be used for submarine communications; however, these bands are limited by the antenna structure required and the bandwidth necessary to transmit information. For this reason, submarines or other submerged craft must either surface or deploy an antenna above the ocean communicate using conventional radio frequency bands. Stealth the primary asset of submerged craft, and it is often impractical for the submerged craft to surface to communicate. Thus it is well known in the art to deploy a positively buoyant tethered buoy to carry an antenna to the surface.
Surfacing and deploying a buoy are impractical for small underwater craft such as underwater vehicles and long range mobile mines. Nevertheless, these craft must surface on occasion to obtain navigational information from the Global Positioning System (GPS) and to communicate with the crafts' base of operations. In order to determine its coordinates, the underwater vehicle receives a code from a GPS satellite which the vehicle uses to determine its coordinates. Depending on the azimuth of the satellite, Global Positioning System data can be obtained in about one minute; however, the underwater device is subject to detection while it is above the surface. Furthermore, surfacing and submerging the underwater vehicle requires that the underwater device contain a large variable buoyancy system to allow the communications portion of the vehicle to break the surface.